Disclosed are a process for hot-dip coating a steel material with a molten aluminum alloy according to a one-stage coating method using a flux which comprises removing an oxide layer on a steel material surface, conducting activating treatment, then coating a chloride flux solution and dipping the steel material in a molten aluminum alloy coating bath floated a fluoride-containing flux, thereby coating the steel material surface with aluminum alloy, or comprises removing an oxide layer on a steel material surface, adjusting surface roughness, conducting activating treatment and dipping the steel material in a molten Al--Zn--Si alloy or Al--Si alloy coating bath floated a flux added an iron component, thereby coating the steel material surface with Al--Zn--Si alloy or Al--Si alloy to adhere a large amount thereof and a aluminum alloy coating bath.